Comparison of hemagglutination inhibition and microbead array assays for the measurement of influenza antibody levels in HIV-infected adults

Introduction: Determining vaccine responsiveness is challenging in immune compromised individuals. The microbead array (MBA) assay is a rapid, inexpensive test for evaluating influenza vaccine immunogenicity. MBA performance was compared to hemagglutination inhibition assay (HAI) utilizing HIV seropositive vaccine recipient specimens.

Methods: CTN 253 evaluated standard dose, single antigen, inactivated split adjuvanted (AS03(A)) H1N1 influenza vaccine (Arepanrix) vs standard dose plus booster. CTN237 evaluated three doses of a seasonal, trivalent killed split non-adjuvanted influenza vaccine (Fluviral). Samples of convenience from 75 CTN 253 and 58 CTN 237 participants were evaluated by MBA and HAI. MBA seroreactivity cut-offs of 500 and 1000 mean fluorescent intensity were used to compare those derived by HAI [titer ≥40 (seroprotection) and 4-fold titer increase from baseline (seroconversion)].

Results: CTN253: Using a MBA cut-off of 500, 75% and 59% had seroreactive titers at visit 2 and 78% and 61% at visit 3 for the single versus double dose study arms. Many participants were categorized differently by the HAI and MBA tests, with raw agreement of 59% at visit 2 and 57% at visit 3. CTN 237: Baseline MBA medians (IQR) were 803 (12-2626) for the A/Brisbane strain and 460 (14-1758) for the B/Florida strain. Using a cut-off of 500 yielded for the A/Brisbane strain seroreactivity rates of 44%, 58%, and 63% were observed for the three doses of vaccine tested. The raw agreement was 47%. B/Florida strain analyses yielded similar results. For all strains assessed in both studies, no relationship between MBA values and baseline variables was identified.

Conclusion: The concordance of results between the MBA assay and the HAI assay is very low. MBA assay may be more sensitive than the HAI assay suggesting that it was either detecting more false-positive results and/or that the HAI assay had more false negative.